In treating toilet flush water with chemicals in order to produce desirable effects such as bowl cleaning, disinfection, deodorization, aerosol reduction, etc., it is desirable that the chemicals be dispensed into the flush water automatically each time the toilet is flushed. The prior art discloses numerous devices which have been designed for this purpose. Exemplary of such devices are those disclosed in U.S. Pat. No. 3,831,205, issued Aug. 27, 1974 to Foley, U.S. Pat. No. 3,341,074 issued Sept. 12, 1967 to Pannutti, U.S. Pat. No. 3,504,384 issued Apr. 7, 1970 to Radley et al., U.S. Pat. No. 2,688,754 issued Sept. 14, 1954 to Willets et al. and U.S. Pat. No. 4,036,407, issued July 19, 1977 to Slone. Particularly desirable devices are those wherein the chemical composition is in the device in the form of a solid cake composition. In this type of device a measured amount of water enters the device during one flush cycle and remains in contact with the cake composition between flushes, thereby forming a concentrated solution of the composition which is dispensed into the flush water during the next flush. Obvious advantages of such devices are that the chemical composition can be packaged and shipped in more concentrated form than aqueous solutions of the chemicals, and the problems of liquid spillage resulting from breakage of the dispensers during shipment or handling is eliminated. Especially preferred devices for automatic dispensing of chemicals from solid cake compositions into the toilet are those described in U.S. Pat. No. 4,171,546 of Dirksing, issued Oct. 23, 1979, U.S. Pat. No. 4,208,747, Dirksing, issued June 24, 1980, U.S. Pat. No. 4,186,856, Dirksing, issued Feb. 5, 1980, and Application U.S. Ser. No. 58,974 of Williams and Owens filed July 20, 1979, all of said applications being incorporated herein by reference.
A particularly desirable component of cake compositions used in the aforedescribed dispensing devices is a surfactant (see Application U.S. Ser. No. 915,027, Kitko, filed June 12, 1978, U.S. Pat. No. 4,200,606, Kitko, issued Apr. 28, 1980 and Application U.S. Ser. No. 153,993, Choy and Greene, entitled "POLY(ETHYLENE OXIDE) COMPOSITIONS WITH CONTROLLED SOLUBILITY CHARACTERISTICS", filed May 28, 1980, all incorporated by reference herein). The surfactants provide cleaning and sudsing in the toilet bowl and also serve to disperse other components of the compositions such as dyes, perfumes, organic resins, etc. in the flush water. Anionic surfactants, especially the organic sulfate and sulfonate types, are particularly desirable for use in these compositions because of their availability, low cost and excellent cleaning and dispersing properties. Water soluble inert salts such as alkali metal chlorides and sulfates are desirably used in such compositions to act as a "filler" or "bulking agent" so that the composition can be formed into cakes or reasonable size without using excessive and wasteful amounts of active ingredients. The predominant ingredients in the cake compositions are usually the surfactant and the filler salt. In concentrated aqueous systems (such as formed within an automatic toilet treating dispenser during the period between flushes), salts often tend to "salt out" anionic surfactants, thereby rendering them insoluble and incapable of performing their intended function. In formulating anionic surfactant-containing cakes for use in automatic toilet dispensing devices it has been found that, in order to avoid a "salting out" effect on the surfactant which would prevent the attainment of the desired concentration of surfactant in solution in the dispenser, it was necessary to use a ratio of surfactant to salt which required the use of much more surfactant than would otherwise be necessary for the surfactant to perform its cleaning and dispersing function if salt were not present. This is wasteful of surfactant.
The object of the present invention is to provide detergent cake formulations which comprise anionic surfactant and salt wherein relatively high levels of salt can be used without reducing the solubility of the surfactant to an unacceptable degree.